The importance of calcium ions in many biological processes is only beginning to be realized. In many proteins and enzymes, calcium ion binding is so specific that even the chemically similar magnesium ion cannot replace it. It has recently been shown, however, that lanthanide ions can replace calcium ions in such systems. Concanavalin A, a protein which possesses hemagglutining activity, requires that calcium ion be bound before its small molecule binding site becomes available. Since the ability of Con A to precipitate small molecules allows it to serve as an idealized model of the antibody-antigen system, studying the calcium ion binding site requirement may help elucidate the role of metal ions in immuno-chemical systems. In addition, this protein provides an ideal system for laying the groundwork for spectroscopic studies of lanthanide ion binding in proteins and enzymes. By applying the techniques of fluorescence spectroscopy, ultraviolet and visible spectroscopy, and nuclear magnetic resonance spectroscopy, distances between the metal binding sites and the small molecule binding site can be calculated. These may be compared with X- ray data to pinpoint differences between the solution structure and the solid state structure of this protein.